Robert Langdon is the protagonist in five of Dan Brown’s books, the most famous being The Da Vinci Code. Each book in the Robert Langdon series follows a similar pattern wherein Langdon must use his background in religious symbology to solve complicated mysteries with real-world consequences while facing down a secret religious or fraternal sect. The books have sold over 200 million copies worldwide. Three of the books (The Da Vinci Code, Angels and Demons, and Inferno) were made into feature-length films starring Tom Hanks and directed by Ron Howard.

In the first book of the series, Angels and Demons, a physicist at the CERN is murdered and marked with an Illuminati symbol. Harvard professor of symbology Robert Langdon is introduced and is called to assess the brand. Along with the physicist’s daughter, Langdon travels to the Vatican to find the killer. In the second book, The Da Vinci Code, Langdon becomes the prime suspect in the murder of the Louvre curator, who dies covered in religious symbols. Along with the curator’s granddaughter, Langdon hunts the real killer while attempting to avoid capture. In the third book, The Lost Symbol, Langdon hunts his friend’s kidnappers, uncovering a freemason legend about a power source similar to God’s natural power.